1. Field of the Invention
The present invention relates to a light-beam heating apparatus which makes local heating possible by condensing light from a radiating lamp and is suitable for heating for soldering, removal of a coating of a fine polyurethane wire, or heating treatment of resin and so forth.
2. Description of the Related Art
A light-beam heating apparatus in which light from a radiating lamp is condensed and made to be incident to one end of an optical fiber, and light emitted from another end thereof is condensed by using an optical system, thereby to heat an article to be heated which is placed in the vicinity of a light condensing point has become to be widely used in recent years. In this apparatus, an ellipsoidal reflecting mirror for reflecting and condensing light is used, a light emitting portion of a radiating lamp is positioned at a first focal point thereof, and a light receiving end of the optical fiber is positioned at a second focal point thereof in order to utilize light energy generated in the radiating lamp effectively.
In such a conventional light-beam heating apparatus, the light emitting portion of the radiating lamp is fixed after adjustment to the position of the first focal point by means of a lamp fitting mechanism when service is commenced. The light emitting portion moves due to thermal expansion of the radiating lamp generated thereafter by light radiation and consumption of an electrode of the radiating lamp. As a result, light energy condensed at the second focal point and incident to the light receiving end of the optical fiber is reduced. Even if the light emitting portion of the radiating lamp is arranged in advance at a position shifted from the first focal point by the lamp fitting mechanism taking thermal expansion and electrode consumption into consideration, the converged light is not correctly focused on the light receiving end of the optical fiber until the radiating lamp reaches a predetermined temperature or after the electrode consumption advances to some degree. As a result, the article to be heated is heated in a state of low light energy, and the light energy of the radiating lamp cannot be utilized effectively. Since electrode consumption proceeds further, the light emitting portion comes off the position of the first focal point and heating conditions of the article to be heated are deteriorated similarly to the above, and the light energy of the radiating lamp cannot be utilized effectively. Furthermore, when the life of the radiating lamp has expired and a new radiating lamp is fitted, it is required to readjust the light emitting portion of the new radiating lamp at the position of the first focal point on all such occasions by means of the lamp fitting mechanism. Namely, in order to heat the article to be heated utilizing the light energy of the radiating lamp effectively, it is required to always adjust the lamp fitting mechanism so as to arrange the light emitting portion of the radiating lamp at the position of the first focal point. Due to low efficiency of such an adjustment, it has been impossible to utilize the light energy of the radiating lamp effectively. Further, it is demanded to hold the light energy for heating the article to be heated at a predetermined intensity and also to realize high reproducibility in order to utilize light-beam heating apparatus for industrial purposes. Thus, such a task as to adjust an electric current of a power supply circuit by means of an output con, hand circuit so as to maintain the light energy at a predetermined value is required. In this task , it is required to suspend the heating operation and to measure and confirm a light-beam output which is outputted from a lens holder provided at opposing end of the optical fiber with a power meter and the like.
In order to have the same operating conditions reappear, such a task has to be perforated every time the above-described fluctuation factor is generated. Since the efficiency of the heating operation is lowered, however, performing this task has not been practical.